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TPS Setting, Importance & Sensitivity

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Hi gentlemen,

 

looking at the last posts it seems there are some misunderstandings about the TPS reset. 

 

[edit: trimmed content. . . . .]

 

Why is the TPS reset or adjustment required, one might ask. Because all things mechanical, such as the throttle shaft bearings or the contact area of the butterfly valve against the throttle body, will wear over time.

 

Why would this minor wear be important, one might ask. Because the inlet area (equivalent to air mass moving through the throttle body) is a cosine function of the throttle shaft and attached butterfly valve. The inital small openings of the butterfly valve  result in (% increase of inlet area) the same values than the latter steps which move from, for example, 40° to 50°. Which is why the TPS breakpoints are clustered up to ~20° and get less dense afterwards. At ~75% of total opening (or WOT -25%) the free inlet area will no longer increase because the throttle shaft area is bigger than the area of the rotated butterfly valve.

 

 

 [edit: trimmed content. . . . .  https://www.v11lemans.com/forums/index.php?showtopic=20649&p=237167  ]

 

Cheers

Meinolf

 

After my recent 5,000 mile/ 8.000 km tune-up, my Sport renewed it's undesirable popping and burbling on the over-run (closed throttle decelerating), idle stumble, with popping and hiccups below 3,500 rpm. But, it really ran like the cliché scalded dog 4,000 to redline. :grin:

 

I had decided to skip the TPS reset and simply adjusted the valves, new plugs, and throttle body balance.  I looked at my notes and see I skipped the TPS last time as well. No good. TPS was 172 mv. I have set it back to 157 mv, but probably will not get to test ride for some time.

 

So, at 172 mv, would this account for why it ran wildly stronger in the upper range and lost its ability to stay stable below 3500? :huh2:

 

[Amended the Decent Tune-up to retain emphasis on this critical step.]

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Hi,

 

So, at 172 mv, would this account for why it ran wildly stronger in the upper range and lost its ability to stay stable below 3500? :huh2:

 

 

I doubt that this is the only reason, but certainly a contributing factor. The ADC used in the 15M is a 8bit, which resolves the 5V to steps of 19,53mV. The delta between 157 and 170mV is 13mV, this equals roughly one ADC step. So the fuel values would slip one row, which is noticeable but not to the extent of what you describe.

 

A re-sync is what I would do.

 

Cheers

Meinolf

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Thanks, Meinolf! Will do a resynch. I noticed several uneven clear spaces in the mercury columns this last time and struggled to get the columns even. I have always assumed this is water that has condensed onto the mercury.

 

Since the bike should be warmed up to synch, I’ll get the chance to see if there is any noticeable change from the TPS adjustment.

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After the good fortune to ride the Sport today (always a joy, but especially in mid-February here!), I was elated to find all of the popping, hiccups, and hesitations gone. The idle was stable without stutters or pops, no lurching or "misfires" moving away from a stop or rolling on out of corners. Gone, also, was the popping and crackling on deceleration. :)

I had a great "long way to work" through the hills and hollers (45 miles).  :race:

 

This outcome is especially satisfying as the only change I made was setting the TPS (Fully closed throttle plate, etc.) from 172 mv to 157 mv.  Idle was still a little low for my tastes, so I checked the Throttle Body Balance (and because I promised Meinolf I would!  :sun: )

I had opened and gently warmed the mercury chamber of my MotionPro "Balance Sticks" to above the dew point to (hopefully) evacuate moisture. The mercury columns rode up solid and clear of gaps. Balance was perfect at "some rpm" (2000-3000), but way off at idle. I brought he RH air bypass screw out 1 & 1/2 turns and the LH is about half that. The mercury settled out evenly and the idle rose and stabilized.

I did not have to move the idle stop screw. :thumbsup:

 

(Disclaimer: I acknowledge that :notworthy:  Meinolf has an expertly crafted map and method to defeat the air bypass entirely.)

 

So, #1) I am impressed the TPS really is that sensitive. It must have been right on the break point where I could not stabilize the tune.  I remember fussing and fussing with the Throttle Body Balance as it would jump back and forth suddenly trying to set the "white knob".

No way I would skip the TPS setting in the Tune-up again (I skipped it twice/ 10,000 miles and it "told on me!" :blush: )

 

And #2) Why do my air bypass screws have to be so different from one another now?

Over 100,000 miles/ 178.000 km and the throttle body shafts and seals are leaking air in that badly? :huh2:

Something with my valves/guides/ heads? 

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On my Tonti FI bikes (I assume the V11 would be similar but with reversed sides) after I set the TPS at 157mV, I turn in the set screw on the TPS side body until it is about 500mV + or - and have the airbleed screws in all the way on both sides with the connecting rod disconnected. I then do idle balance with the set screws on both bodies and then reconnect the rod and then do a balance at about 3000RPM.

It is possible that you have leaky shafts and seals too or differences in compression.

It seems best to me to balance at idle with the set screws. The balance may compensate for some of the wear irregularities. 

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It occurred to me I can spray some solvent or cleaner on the underside of the shafts while its idling and see if the idle changes just like looking for any vacuum leak . . .

 

Using the air screws to balance the idle has always seen mine a bout 1/4 off from each other, but this is a big change just lately. I mean, it is idling fine and runs great, just keeping an eye on things and wanting to know what to expect from the old girl.

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So, yep. When I saturate the bottom of the left throttle body through the spring, the idle falters significantly. Throttle shaft is pretty wobbly, as well. :mellow:

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Hi gentlemen,

 

looking at the last posts it seems there are some misunderstandings about the TPS reset. 

 

[edit: trimmed content. . . . .]

 

Why is the TPS reset or adjustment required, one might ask. Because all things mechanical, such as the throttle shaft bearings or the contact area of the butterfly valve against the throttle body, will wear over time.

 

Why would this minor wear be important, one might ask. Because the inlet area (equivalent to air mass moving through the throttle body) is a cosine function of the throttle shaft and attached butterfly valve. The inital small openings of the butterfly valve  result in (% increase of inlet area) the same values than the latter steps which move from, for example, 40° to 50°. Which is why the TPS breakpoints are clustered up to ~20° and get less dense afterwards. At ~75% of total opening (or WOT -25%) the free inlet area will no longer increase because the throttle shaft area is bigger than the area of the rotated butterfly valve.

 

 

 [edit: trimmed content. . . . .  https://www.v11lemans.com/forums/index.php?showtopic=20649&p=237167  ]

 

Cheers

Meinolf

 

After my recent 5,000 mile/ 8.000 km tune-up, my Sport renewed it's undesirable popping and burbling on the over-run (closed throttle decelerating), idle stumble, with popping and hiccups below 3,500 rpm. But, it really ran like the cliché scalded dog 4,000 to redline. :grin:

 

I had decided to skip the TPS reset and simply adjusted the valves, new plugs, and throttle body balance.  I looked at my notes and see I skipped the TPS last time as well. No good. TPS was 172 mv. I have set it back to 157 mv, but probably will not get to test ride for some time.

 

So, at 172 mv, would this account for why it ran wildly stronger in the upper range and lost its ability to stay stable below 3500? :huh2:

 

[Amended the Decent Tune-up to retain emphasis on this critical step.]

 

Your fuel map would think you have the throttle open farther, give more fuel and richen the mixture. Perhaps you're a little lean up top normally.

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